1. Field of the Invention
The present invention relates to an image forming apparatus, and more particularly, to an image forming apparatus such as a copying machine or the like which is provided with a paper feed tray having an elevator that can move up and down between lowest position and a paper feed position positioned above the lowest position, so that paper is set on the elevator when the elevator is at the lowest position, and is fed to the image forming apparatus when the elevator is at the paper feed position.
2. Description of the Related Art
A copying machine has been known to those skilled in the art to be provided with a paper feed tray (referred to as an LCT hereinafter) for storing a plenty of copying papers with up-and-down movements of an elevator for setting them thereon.
In this kind of the copying machine, the LCT is raised by an elevator to a paper feed position when the power switch is turned ON, and lowered to the lowest position or a paper supply position in which papers are supplied to the LCT, when the power switch is turned OFF. Moreover, when a cover of the LCT is opened and an elevator down key is depressed to supply paper to be copied onto the elevator within the LCT, the elevator is lowered to the lowest position. Thereafter, when the cover of the LCT is closed after being supplied with paper, the elevator is automatically raised to the paper feed position.
In such a conventional copying machine described as above, it is impossible to feed the paper from the LCT while the elevator is driven, namely, moving up and down. Therefore, the copying machine at this occasion is forced into a paper empty state, that is, in a state lack of papers in the LCT.
Even if a print key is depressed after depressing a key for selecting the LCT in order to perform a copying operation during rising of the elevator, it may be in a paper empty state. Then, the LCT can not be selected. In order to start the copying operation, it is necessary to depress the print key again after waiting until the elevator reaches the paper feed position. In this case, it takes a long time to operate the copying machine and perform the copying operation.
Furthermore, when the print key is manipulated during the rising time of the elevator in an automatic paper selecting mode (referred to as an APS mode hereinafter), even if the size of the paper set in the LCT is proper to a document, the LCT is switched to another tray because of the above-mentioned paper empty state. Therefore, it sometimes happens that copying is achieved on a paper of an improper size.